Method of producing sodium tetraborate tetrahydrate



necessary to dissolve borax ore.

METHOD OF PRODUCING SODIUM TETRA- BORATE TETRAHYDRATEj Vincent Morgan, Boron, Calif., assignor to United States Borax & Chemical Corporation, Los Angeles, Calif., a corporation of Nevada No Drawing. Filed Apr. 15, 1958, Ser. No. 728,545,

2 Claims. (Cl.2359).

This invention relates as indicated to a method for producing sodium tetraborate tetrahydrate and has more particular reference to a method for synthetically producing kernite (Na B O -4H O) from water solution at atmospheric pressure. 1

The mineral kernite ('Na B O -4H O) is known to be naturally occurring, and at one time was the major borate ore used in the production of borax, boricacid, etc. However, while kernite was used to produce refined borax (Na B O -lI-I O), refined substantially pure crystals of kernite (Na l3 0 -4H O) have never been produced.

Over the years the kernite deposits have been used less and less and the present principal borate source is now borax (Na B 0 -10H O). With the increasing interest of supplying a slowly soluble borate material for agricultural purposes, anew interest has again been aroused in kernite. 'Besidesthe advantage of slow water solubility; kernite has the additional advantages of greater density and of only containing 4 mols of water which is quite obviously a shipping advantage over 10 mol or even 5 mol borax.

Many futile attempts have been made to synthetically produce kernite from borax at atmospheric pressure. The only known synthesis of kernite was accomplished under laboratory conditions by the use of high tempera tures and pressures over long periods of time. Even with the foregoing ideal laboratory conditions the resultant product contained some 5 mol borax.

The main reason that Na B O -H O ore is used instead of kernite ore is that kernite is so insoluble and difficult to refine. High temperature and autoclaves are necessary in the dissolution of kernite, whereas relatively simple straightforward hot water solution is all that is Thus it would be extremely desirable if kernite could be produced synthetically at will from borax ore using the same plane equipment.

It is therefore the principal object of the present invention to provide a method for producing a substantially pure synthetic kernite (Na B 0 -4H 0) from borax ore.

A further object of this invention is to provide a method for producing kernite at atmospheric pressure.

Other objects will become apparent as the description proceeds.

To the accomplishments of the foregoing and related ends, the invention then comprises the features herein after fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the ways in which the principle of the invention may be employed.

Broadly stated the present invention comprises the method of synthetically producing kernite which comprises preparing an aqueous solution containing at least 28.0% by weight of Na B O -10H 0, heating the solution to at least 57.5 C., seeding said solution with a minor amount of kernite crystals and continuing the heat ing until kernite crystallizes from said solution.

Thus, contrary to the teachings of the prior art, I have found that kernite can be prepared synthetically from borax providing certain conditions are maintained. First, an aqueous solution must be used which contains at least 28.0% by weight of borax, and secondly, the temperature of the borax solution must be at a temperature of at least v As stated, kernite must be crystallized from solutions containing at least 28% Na B O -10H O. This means that kernite can be crystallized from a 28% solution up to and including a 100% solution of the 10 mol borax. If 10 mol borax is dissolved in its own water of hydration this solution can be used for the crystallization of kernite. I

According to theprocess of the present invention the 4 mol hydrate of sodium tetraborate may be prepared by first formingthe 5 mole hydrate and then redissolving the .5 .mole hydrate in a solution saturated with respect to the 5 mol hydrate and then crystallizing'out the 4 mol hydrate, or it may be crystallized directly from aqueous solution without having the 5 mol present at any time.

So that the present invention may be more clearly understood, the. following examples are offered by way of illustration.

A 60% borax solution was made by heating 300 grams of Na B O-rl0H O with.200 ml. of H 0 in a flask. The flask was fitted with a condenser and heated for about 18 hours at 100 C;

After about 18 hours the 5 mol hydrate, Na B O -5H O crystallized from solution. The mixture was then seeded with about 0.10 gram of natural'kernite and the heating continued.

At the end of about 62 hours total heating time a large crystalline mass was formed at the bottom of the flask. The crystals were filtered, washed with hot water and isopropyl alcohol, and then air-dried.

The crystals were chemically, microscopically analyzed,

and additionally an X-ray powder pattern was made. The analysis provided conclusively that the product of the aforegoing example was substantially pure crystals of kernite.

A chemical analysis revealed the following results:

Percent found Theoretical in Sample 4 mol B201 50. s4 50. 96 Na O 22. e7 22. 68

A solution of 10 mol borax in water was prepared which assayed 55% borax. The solution was seeded with about 0.10 gram of natural kernite and the flask was equipped with a condenser and stirrer. The flask was heated and maintained at a temperature of 91 C. Samples were studied at 18 hours and 25 hours" total elapsed time. No crystals of 5 mol borax were found in the Patented May 9, 1961 3 solution. After 67 hours the solution was-filtered. and the crystals washed and dried.

A chemical analysis gave the following results:

Peroentiound- Theoretical insernple i 4mo l Bios 50.9.4 1 .soos, NajO 22.70 22,68

The foregoing experiments illustrate that the; 4 mol hydrate of sodium tetraborate may be, prepared directly,

the following claims. or the. equivalent. of, such be. em.- ployed.

I, therefore, particularly point out and distinctly claim as my invention:

1. The method of synthetically producing kernite which comprises preparing an aqueous solution containing at least 28.0% by weight of Na B O. .-1 0H O, heating the solution under atmospheric pressure in a temperature from the 10 mol borax or it can be prepared from the I 10 mol borax byfirst going. through the, Simol banal; stage hydrates, and wasof a'pasty'consisteney. Heating was continued until a total of 50 hours had elapsed, when" the contents of the flask were. removed, washed with hot water and isopropyl alcohol, and dried at room temperature. Microscopic (optical) eX3mll'1fiIiQn;.$h0W6d the re-. coveredv material to be. substantially, purefkernitef An analysis of the recovered material is given belqwz.

Bercent found Theoretical 4 mol 1 in Sample.

Other modes of applying'the principle of the invention may be employed, change being made as regards the details described, provided the features stated in anyof range of from 57.5 C. to about 100 C., seeding said solution with a minor amount'ofkernite. crystals and continuing the heating until conversionof theto the tetrahydrate form is substantially complete and the desired synthetic kernite crystallizes out of said solution.

2. The method of synthetically producing kernite which comprises preparing. an: aqueous; solution. containing at least, 28%? by: weightof; N 3zB4Q'z: .QH2Q,. heating: said; solution. under; atmospheric. pr ssure in a temp rature rang 0ffrom575 Cat bout. 1 0?-'C,. ..nti1;

N s eow' i z crystallizes-out of solution, seeding; the mixture withaminor amount of Na B O -4H O, and continuing; said.-

heating until the-Na B Q 5H Q-redissolvesand crystallizes out; of solution.

ReferencesCited i111 the file of this patent UNITED, sIAIEs. PATENTS.

OTHER REFERENCES Thorpes Dictionary of AppliedChemistry," vol. 2,

4th ed., 1938, page 49, Longmans, Green andCo Ne York, NY. 7 I

Crystallization of Boraxj by Donald E. Garrett and Gerhard P. Rosenbaum, Ind; and Eng. Chem, November 1958, vol. 50, No. 11, pages1681-1684.

Allen Mar; 3; 1936' Suhr' Mar; 13,1956 

2. THE METHOD OF SYNTHETICALLY PRODUCING KERNITE WHICH COMPRISES PREPARING AN AQUEOUS SOLUTION CONTAINING AT LEAST 28% BY WEIGHT OF NA2B4O7.10H2O, HEATING SAID SOLUTION UNDER ATMOSPHERIC PRESSURE IN A TEMPERATURE RANGE OF FROM 57.5*C. TO ABOUT 100*C. UNTIL 